Main body structure of a thin film transistor liquid crystal display (TFT-LCD) comprises an array substrate, a backlight and a drive circuit board.
The array substrate of the TFT-LCD is of a layered structure formed by arranging a gate line, a gate insulating layer, an active layer, a source electrode, a drain electrode, a data line, a passivation layer and a pixel electrode on a transparent glass substrate, and is divided into a display region and a peripheral circuit region located in a periphery of the display region, wherein the peripheral circuit region is used for setting a data line driving integrated circuit or a gate line driving integrated circuit.
At present, tests on the array substrate include device performance test for thin film transistor (TFT) and test for electrical properties such as stray capacitance between films. Because both pixel and circuits on the array substrate are encapsulated internally after the array substrate is completed, it is impossible to directly implement contact measurement on TFT performance after the liquid crystal cell is formed as well as electrical properties such as capacitance in the liquid crystal cell. Conventional TFT performance tests are generally finished through setting test units for capacitance, resistance and the like on blank region of the TFT substrate to acquire capacitance, resistance and other electrical properties on TFT and TFT component; performance parameter in pixel on the TFT substrate can be acquired through testing the test unit because the test unit and the TFT are formed by the same technology. However, the films may be scratched by a test probe, that is, pixels may be damaged by the method, and accordingly, this method is only suitable for testing pixel electrical properties before coating alignment layer (Polyimide film, i.e., PI film). In practice, after the liquid crystal cell is formed, due to existence of the PI film, electrical properties inside the array substrate can be actually reflected through electrical properties of the liquid crystal layer and the like (working state or non-working state). By using the test method mentioned above, it is impossible to acquire performance parameters of the tested TFT after liquid crystal cell is formed by bonding the array substrate and the color film substrate, as well as performance indexes such as internal capacitance of the liquid crystal cell. However, TFT performance after forming the liquid crystal cell and electrical data such as internal capacitance of the liquid crystal cell, are quite important for performance assessment and improvement of the liquid crystal display device. Therefore, a method is required to acquire the electrical data.